One of the objectives aimed at in the development of elevators has been an efficient and economic use of building space. In conventional traction-sheave driven elevators, the elevator machine room or other space reserved for the drive machinery takes up a considerable portion of the building space required by the elevator. The problem is not only the volume of the building space needed for the elevator, but also its location in the building. There are numerous solutions to the placement of the machine room, but they generally significantly restrict the design of the building at least in respect of space utilization or appearance. For example, for an elevator with the machine placed beside the bottom part of the shaft, the building has to be provided with a machine room or space placed beside the shaft, generally on the lowest floor served by the elevator. Being a special space, the machine room generally involves increased building costs.
With respect to utilization of space, hydraulic elevators are relatively advantageous, and they often allow the entire drive machine to be placed in the elevator shaft. Hydraulic elevators are applicable in cases where the lifting height is one floor or at most a few floors. In practice, hydraulic elevators cannot be constructed for very large heights.